From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx173.postini.com [74.125.245.173]) by kanga.kvack.org (Postfix) with SMTP id 28BA16B0031 for ; Wed, 11 Sep 2013 22:10:15 -0400 (EDT) Received: by mail-lb0-f178.google.com with SMTP id z5so318964lbh.23 for ; Wed, 11 Sep 2013 19:10:13 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1378805550-29949-28-git-send-email-mgorman@suse.de> References: <1378805550-29949-1-git-send-email-mgorman@suse.de> <1378805550-29949-28-git-send-email-mgorman@suse.de> Date: Thu, 12 Sep 2013 10:10:13 +0800 Message-ID: Subject: Re: [PATCH 27/50] mm: numa: Scan pages with elevated page_mapcount From: Hillf Danton Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: Peter Zijlstra , Rik van Riel , Srikar Dronamraju , Ingo Molnar , Andrea Arcangeli , Johannes Weiner , Linux-MM , LKML Hillo Mel On Tue, Sep 10, 2013 at 5:32 PM, Mel Gorman wrote: > Currently automatic NUMA balancing is unable to distinguish between false > shared versus private pages except by ignoring pages with an elevated > page_mapcount entirely. This avoids shared pages bouncing between the > nodes whose task is using them but that is ignored quite a lot of data. > > This patch kicks away the training wheels in preparation for adding support > for identifying shared/private pages is now in place. The ordering is so > that the impact of the shared/private detection can be easily measured. Note > that the patch does not migrate shared, file-backed within vmas marked > VM_EXEC as these are generally shared library pages. Migrating such pages > is not beneficial as there is an expectation they are read-shared between > caches and iTLB and iCache pressure is generally low. > > Signed-off-by: Mel Gorman > --- [...] > @@ -1658,13 +1660,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm, > int page_lru = page_is_file_cache(page); > > /* > - * Don't migrate pages that are mapped in multiple processes. > - * TODO: Handle false sharing detection instead of this hammer > - */ > - if (page_mapcount(page) != 1) > - goto out_dropref; > - Is there rmap walk when migrating THP? > - /* > * Rate-limit the amount of data that is being migrated to a node. > * Optimal placement is no good if the memory bus is saturated and > * all the time is being spent migrating! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org